U.S. patent application number 16/567025 was filed with the patent office on 2020-03-12 for wound therapy system with instillation therapy and dynamic pressure control.
The applicant listed for this patent is KCI LICENSING, INC.. Invention is credited to Christopher A. Carroll, Shannon C. Ingram, Brett L. Moore, Justin Rice.
Application Number | 20200078224 16/567025 |
Document ID | / |
Family ID | 68051978 |
Filed Date | 2020-03-12 |
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United States Patent
Application |
20200078224 |
Kind Code |
A1 |
Carroll; Christopher A. ; et
al. |
March 12, 2020 |
WOUND THERAPY SYSTEM WITH INSTILLATION THERAPY AND DYNAMIC PRESSURE
CONTROL
Abstract
A wound therapy system includes a dressing an instillation pump
fluidly communicable with the dressing and configured to provide
instillation fluid to the dressing, a negative pressure pump
fluidly communicable with the dressing and configured to remove air
from the dressing, and a control circuit communicably coupled to
the instillation pump and the negative pressure pump. The control
circuit is configured to control the instillation pump to provide
an amount of the instillation fluid to the dressing, provide a soak
period, and control the negative pressure pump to provide a cyclic
variation of negative pressure at the dressing.
Inventors: |
Carroll; Christopher A.;
(San Antonio, TX) ; Moore; Brett L.; (San Antonio,
TX) ; Ingram; Shannon C.; (Bulverde, TX) ;
Rice; Justin; (San Antonio, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KCI LICENSING, INC. |
San Antonio |
TX |
US |
|
|
Family ID: |
68051978 |
Appl. No.: |
16/567025 |
Filed: |
September 11, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62730214 |
Sep 12, 2018 |
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62744759 |
Oct 12, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 2205/3344 20130101;
A61M 1/0088 20130101; A61M 1/0031 20130101; A61M 1/009 20140204;
A61M 1/0062 20130101; A61M 1/0084 20130101; A61M 2205/3379
20130101; A61M 3/0258 20130101; A61F 13/0216 20130101 |
International
Class: |
A61F 13/02 20060101
A61F013/02; A61M 1/00 20060101 A61M001/00 |
Claims
1. A wound therapy system, comprising: a dressing; an instillation
pump fluidly communicable with the dressing and configured to
provide instillation fluid to the dressing; a negative pressure
pump fluidly communicable with the dressing and configured to
remove air from the dressing; and a control circuit communicably
coupled to the instillation pump and the negative pressure pump and
configured to: control the instillation pump to provide an amount
of the instillation fluid to the dressing; provide a soak period;
and control the negative pressure pump to provide a cyclic
variation of negative pressure at the dressing.
2. The wound therapy system of claim 1, wherein the cyclic
variation of negative pressure comprises an oscillation of the
pressure at the dressing across a pressure differential.
3. The wound therapy system of claim 2, wherein the pressure
differential is approximately 100 mmHg.
4. The wound therapy system of claim 3, wherein the pressure
differential is within a range between approximately 5 mmHg and 300
mmHg.
5. The wound therapy system of claim 2, wherein the cyclic
variation of negative pressure comprises a first cycle and a second
cycle; and wherein the pressure differential changes between the
first cycle and the second cycle.
6. The wound therapy system of claim 2, wherein the pressure
differential oscillates over time.
7. The wound therapy system of claim 2, wherein the pressure
differential is user-selectable.
8. The wound therapy system of claim 1, wherein a frequency of the
cyclic variation of negative pressure is user-selectable.
9. The wound therapy system of claim 1, wherein the dressing
comprises a perforated layer comprising a plurality of holes
extending therethrough.
10. The wound therapy system of claim 8, wherein the dressing is
coupleable to a wound bed; and wherein the cyclic variation of
negative pressure deforms the wound bed at the holes.
11. The wound therapy system of claim 8, wherein the cyclic
variation of negative pressure comprises a plurality of cycles; and
wherein each cycle does an amount of work of within a range between
approximately 2 mJ and 30 mJ for each of the plurality of
holes.
12. The wound therapy system of claim 1, wherein the control
circuit is configured to simultaneously control the negative
pressure pump to provide a cyclic variation of negative pressure at
the dressing and control the instillation pump to provide the
instillation fluid to the dressing.
13. The wound therapy system of claim 1, wherein at least one of
the amount of the instillation fluid or the soak period are
user-selectable.
14. The wound therapy system of claim 1, wherein the control
circuit is further configured to control the negative pressure pump
to provide a substantially constant negative pressure at the
dressing.
15. The wound therapy system of claim 1, wherein the control
circuit is further configured to repeatedly cycle through
sequentially controlling the instillation pump to provide the
amount of the instillation fluid to the dressing, providing the
soak period, and controlling the negative pressure pump to provide
the cyclic variation of negative pressure at the dressing.
16. The wound therapy system of claim 1, wherein the control
circuit is further configured to repeatedly cycle through
sequentially controlling the instillation pump to provide the
amount of the instillation fluid to the dressing, providing the
soak period, controlling the negative pressure pump to provide the
cyclic variation of negative pressure at the dressing, and
controlling the negative pressure pump to provide a substantially
constant negative pressure to the wound bed.
17. A method of treating a wound, comprising: providing an
instillation pump in fluid communication with a dressing; providing
a negative pressure pump in fluid communication with the dressing;
supplying, by the instillation pump, an amount of instillation
fluid to the dressing; waiting for a soak period; and operating the
negative pressure pump to create a cyclic variation of negative
pressure at the dressing.
18. The method of claim 17, wherein the cyclic variation of
negative pressure comprises an oscillation of the pressure at the
dressing across a pressure differential.
19. The method of claim 18, wherein the pressure differential is
approximately 100 mmHg.
20. The method of claim 17, wherein the pressure differential is in
a range between approximately 5 mmHg and 300 mmHg.
21. The method of claim 18, wherein the cyclic variation of
negative pressure comprises a first cycle and a second cycle; and
the method comprises changing the pressure differential between the
first cycle and the second cycle.
22. The method of claim 18, comprising oscillating the pressure
differential over time.
23. The method of claim of claim 18, comprising receiving a user
selection of the pressure differential.
24. The method of claim 17, comprising receiving a user selection
of a frequency of the cyclic variation of negative pressure.
25. The method of claim 17, comprising deforming, by the cyclic
variation of negative pressure, a wound bed coupled to the
dressing.
26. The method of claim 24, wherein deforming the wound bed
comprises drawing the wound bed into a plurality of holes that
extend through a layer of the dressing.
27. The method of claim 25, comprising doing an amount of work on
the wound bed within a range between approximately 2 mJ and 30 mJ
for each of the plurality of holes for each of multiple cycles of
the cyclic variation of negative pressure.
28. The method of claim 17, comprising simultaneously operating the
negative pressure pump to create a cyclic variation of negative
pressure at the dressing and controlling the instillation pump to
provide the instillation fluid to the dressing.
29. The method of claim 17, comprising receiving a user selection
of at least one of the amount of the instillation fluid or the soak
period.
30. The method of claim 17, comprising operating the negative
pressure pump to create a substantially constant negative pressure
at the dressing.
31. The method of claim 19, comprising repeatedly cycling through
sequentially supplying, by the instillation pump, an amount of
instillation fluid to the dressing, waiting for a soak period, and
operating the negative pressure pump to create a cyclic variation
of negative pressure at the dressing.
32. The method of claim 17, comprising repeatedly cycling through
sequentially supplying, by the instillation pump, an amount of
instillation fluid to the dressing, waiting for a soak period,
operating the negative pressure pump to create a cyclic variation
of negative pressure at the dressing, and operating the negative
pressure pump to create a substantially constant negative pressure
at the dressing.
33. A wound therapy system, comprising: a dressing; an instillation
pump fluidly communicable with the dressing and configured to
provide instillation fluid to the dressing; a negative pressure
pump fluidly communicable with the dressing and configured to
remove air from the dressing; and a control circuit communicably
coupled to the instillation pump and the negative pressure pump and
configured to: control the instillation pump to provide an amount
of the instillation fluid to the dressing; provide a soak period;
and control the negative pressure pump to provide a variation of
negative pressure at the dressing, the variation characterized by a
waveform.
34. The wound therapy system of claim 33, wherein the waveform
comprises: an amplitude having a maximum at a high pressure value
and a minimum at a low pressure value; and a frequency.
35. The wound therapy system of claim 34, wherein the amplitude is
variable in a repeating pattern.
36. The wound therapy system of claim 34, wherein the frequency is
variable in a repeating pattern.
37. The wound therapy system of claim 34, wherein: the amplitude is
variable in a first repeating pattern; and the frequency is
variable in a second repeating pattern.
38. The wound therapy system of claim 33, wherein the waveform is
user-selectable.
39. The wound therapy system of claim 33, wherein the control
circuit is configured to simultaneously control the negative
pressure pump to provide the variation of negative pressure at the
dressing and control the instillation pump to provide the
instillation fluid to the dressing.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority to U.S.
Provisional Application No. 62/730,214, filed on Sep. 12, 2018, and
U.S. Provisional Application No. 62/744,759, filed on Oct. 12,
2018, which are both incorporated herein by reference in their
entireties.
BACKGROUND
[0002] The present invention relates generally to the field of
treating wounds, and more particularly to negative pressure wound
therapy systems with instillation therapy. Negative pressure wound
therapy refers to the application of negative pressure (relative to
atmospheric pressure) to a wound bed to facilitate healing of the
wound bed. Negative pressure may be applied in coordination with
instillation therapy, in which instillation fluid (e.g., cleansing
fluid, medicated fluid, antibiotic fluid, irrigation fluid) is
applied to the wound bed. Negative pressure therapy with
instillation therapy may facilitate removal of wound exudate and
other debris from the wound bed and otherwise support healing. The
present disclosure provides improved systems and methods for
treating wounds using negative pressure wound therapy and
instillation therapy.
SUMMARY
[0003] One implementation of the present disclosure is a wound
therapy system. The wound therapy system includes a dressing an
instillation pump fluidly communicable with the dressing and
configured to provide instillation fluid to the dressing, a
negative pressure pump fluidly communicable with the dressing and
configured to remove air from the dressing, and a control circuit
communicably coupled to the instillation pump and the negative
pressure pump. The control circuit is configured to control the
instillation pump to provide an amount of the instillation fluid to
the dressing, provide a soak period, and control the negative
pressure pump to provide a cyclic variation of negative pressure at
the dressing.
[0004] In some embodiments, the cyclic variation of negative
pressure includes an oscillation of the pressure at the dressing
across a pressure differential. In some embodiments, the pressure
differential is approximately 100 mmHg. In some embodiments, the
pressure differential is within a range between approximately 5
mmHg and 300 mmHg.
[0005] In some embodiments, the cyclic variation of negative
pressure includes a first cycle and a second cycle. The pressure
differential changes between the first cycle and the second cycle.
In some embodiments, the pressure differential oscillates over
time.
[0006] In some embodiments, the pressure differential is
user-selectable. In some embodiments, a frequency of the cyclic
variation of negative pressure is user-selectable.
[0007] In some embodiments, the dressing includes a perforated
layer having a plurality of holes extending therethrough. In some
embodiments, the dressing is coupleable to a wound bed. The cyclic
variation of negative pressure deforms the wound bed at the holes.
In some embodiments, the cyclic variation of negative pressure
includes a plurality of cycles. Each cycle does an amount of work
of within a range between approximately 2 mJ and 30 mJ for each of
the plurality of holes.
[0008] In some embodiments, the control circuit is configured to
simultaneously control the negative pressure pump to provide a
cyclic variation of negative pressure at the dressing and control
the instillation pump to provide the instillation fluid to the
dressing.
[0009] In some embodiments, at least one of the amount of the
instillation fluid or the soak period is user-selectable. In some
embodiments, the control circuit is further configured to control
the negative pressure pump to provide a substantially constant
negative pressure at the dressing.
[0010] In some embodiments, the control circuit is further
configured to repeatedly cycle through sequentially controlling the
instillation pump to provide the amount of the instillation fluid
to the dressing, providing the soak period, and controlling the
negative pressure pump to provide the cyclic variation of negative
pressure at the dressing. In some embodiments, the control circuit
is further configured to repeatedly cycle through sequentially
controlling the instillation pump to provide the amount of the
instillation fluid to the dressing, providing the soak period,
controlling the negative pressure pump to provide the cyclic
variation of negative pressure at the dressing, and controlling the
negative pressure pump to provide a substantially constant negative
pressure to the wound bed.
[0011] Another implementation of the present disclosure is a method
of treating a wound. The method includes providing an instillation
pump in fluid communication with a dressing, providing a negative
pressure pump in fluid communication with the dressing, supplying,
by the instillation pump, an amount of instillation fluid to the
dressing, waiting for a soak period, and operating the negative
pressure pump to create a cyclic variation of negative pressure at
the dressing.
[0012] In some embodiments, the cyclic variation of negative
pressure includes an oscillation of the pressure at the dressing
across a pressure differential. In some embodiments, the pressure
differential is approximately 100 mmHg. In some embodiments, the
pressure differential is in a range between approximately 5 mmHg
and 300 mmHg.
[0013] In some embodiments, the cyclic variation of negative
pressure includes a first cycle and a second cycle. The method
includes changing the pressure differential between the first cycle
and the second cycle. In some embodiments, the method includes
oscillating the pressure differential over time. In some
embodiments, the method includes receiving a user selection of the
pressure differential. In some embodiments, the method includes
receiving a user selection of a frequency of the cyclic variation
of negative pressure.
[0014] In some embodiments, the method includes deforming, by the
cyclic variation of negative pressure, a wound bed coupled to the
dressing. In some embodiments, deforming the wound bed includes
drawing the wound bed into a plurality of holes that extend through
a layer of the dressing. In some embodiments, the method includes
doing an amount of work on the wound bed within a range between
approximately 2 mJ and 30 mJ for each of the plurality of holes for
each of multiple cycles of the cyclic variation of negative
pressure.
[0015] In some embodiments, the method includes simultaneously
operating the negative pressure pump to create a cyclic variation
of negative pressure at the dressing and controlling the
instillation pump to provide the instillation fluid to the
dressing.
[0016] In some embodiments, the method includes receiving a user
selection of at least one of the amount of the instillation fluid
or the soak period. In some embodiments, the method includes
operating the negative pressure pump to create a substantially
constant negative pressure at the dressing.
[0017] In some embodiments, the method includes repeatedly cycling
through sequentially supplying, by the instillation pump, an amount
of instillation fluid to the dressing, waiting for a soak period,
and operating the negative pressure pump to create a cyclic
variation of negative pressure at the dressing.
[0018] In some embodiments, the method includes repeatedly cycling
through sequentially supplying, by the instillation pump, an amount
of instillation fluid to the dressing, waiting for a soak period,
operating the negative pressure pump to create a cyclic variation
of negative pressure at the dressing, and operating the negative
pressure pump to create a substantially constant negative pressure
at the dressing.
[0019] Another implementation of the present disclosure is a wound
therapy system. The wound therapy system includes an instillation
pump fluidly communicable with the dressing and configured to
provide instillation fluid to the dressing, a negative pressure
pump fluidly communicable with the dressing and configured to
remove air from the dressing, and a control circuit communicably
coupled to the instillation pump and the negative pressure pump.
The control circuit is configured to control the instillation pump
to provide an amount of the instillation fluid to the dressing,
provide a soak period, and control the negative pressure pump to
provide a variation of negative pressure at the dressing, the
variation characterized by a waveform.
[0020] In some embodiments, the waveform includes an amplitude
having a maximum at a high pressure value and a minimum at a low
pressure value and a frequency. In some embodiments, the amplitude
is variable in a repeating pattern. In some embodiments, the
frequency is variable in a repeating pattern. In some embodiments,
the amplitude is variable in a first repeating pattern and the
frequency is variable in a second repeating pattern. In some
embodiments, the waveform is user-selectable.
[0021] In some embodiments, the control circuit is configured to
simultaneously control the negative pressure pump to provide the
variation of negative pressure at the dressing and control the
instillation pump to provide the instillation fluid to the
dressing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a perspective view of a negative pressure and
instillation wound therapy system, according to an exemplary
embodiment.
[0023] FIG. 2 is a block diagram of the negative pressure and
instillation wound therapy system of FIG. 1, according to an
exemplary embodiment.
[0024] FIG. 3 is an illustration of negative pressure waveforms,
according to an exemplary embodiment.
[0025] FIG. 4 is a flowchart of a process for negative pressure and
instillation wound therapy, according to an exemplary
embodiment.
[0026] FIG. 5 is an illustration of experimental results using the
process of FIG. 4 with the negative pressure and instillation wound
therapy system of FIG. 1, according to an exemplary embodiment.
[0027] FIG. 6 is a cross-sectional side view of a dressing for use
with the negative pressure and instillation wound therapy system of
FIG. 1, according to an exemplary embodiment.
[0028] FIG. 7 is a bottom view of a dressing for use with the
negative pressure and instillation wound therapy system of FIG. 1,
according to an exemplary embodiment.
[0029] FIG. 8 is a depiction of wound deformation under negative
pressure using the dressing of FIGS. 6-7, according to an exemplary
embodiment.
[0030] FIG. 9 is a flowchart of a process for negative pressure and
instillation wound therapy, according to an exemplary
embodiment.
[0031] FIG. 10 is a graphical representation of a negative pressure
waveform with hold periods, according to an exemplary
embodiment.
[0032] FIG. 11 is a graphical representation of an aggressive
cleanse negative pressure waveform, according to an exemplary
embodiment.
[0033] FIG. 12 is a graphical representation of a negative pressure
waveform with an oscillating high pressure value, according to an
exemplary embodiment.
DETAILED DESCRIPTION
Negative Pressure and Instillation Wound Therapy System
[0034] Referring to FIGS. 1 and 2, a negative pressure and
instillation wound therapy (NPIWT) system 100 is shown, according
to exemplary embodiments. FIG. 1 shows a perspective view of the
NPIWT system 100, according to an exemplary embodiment. FIG. 2
shows a block diagram of the NPIWT system 100, according to an
exemplary embodiment. The NPIWT system 100 is shown to include a
therapy unit 102 fluidly coupled to a dressing 104 via a vacuum
tube 106 and an instillation tube 108. The NPIWT system 100 is also
shown to include an instillation fluid source 110 fluidly coupled
to the instillation tube 108. The NPIWT system 100 is configured to
provide negative pressure wound therapy at a wound bed by reducing
the pressure at the dressing 104 relative to atmospheric pressure.
The NPIWT system 100 is also configured to provide instillation
therapy by providing instillation fluid to the dressing 104.
Furthermore, as described in detail herein, the NPIWT system 100 is
configured to provide debridement of the wound bed and removal of
undesirable fluid and debris from the wound bed.
[0035] The dressing 104 is coupleable to a wound bed, i.e., a
location of a wound (e.g., sore, laceration, burn, etc.) on a
patient. The dressing 104 may be substantially sealed over the
wound bed such that a pressure differential may be maintained
between the atmosphere and the wound bed (i.e., across the dressing
104). The dressing 104 may be coupled to the vacuum tube 106 and
the instillation tube 108, for example to place the vacuum tube 106
and/or the instillation tube 108 in fluid communication with the
wound bed. An example embodiment of dressing 104 is shown in FIGS.
6-7 and described in detail with reference thereto. In some
embodiments, the dressing 104 may be a V.A.C. VERAFLO.TM. dressing
by Acelity or a V.A.C. VERAFLO CLEANSE CHOICE.TM. dressing by
Acelity.
[0036] The therapy unit 102 includes a negative pressure pump 112
(shown in FIG. 2 and obscured within the therapy unit 102 in the
perspective view of FIG. 1) configured to pump air, wound exudate,
and/or other debris (e.g., necrotic tissue) and/or fluids (e.g.,
instillation fluid) out of the dressing 104 via the vacuum tube
106, thereby creating a negative pressure at the dressing 104. The
negative pressure pump 112 is fluidly communicable with the vacuum
tube 106 and the dressing 104. Wound exudate and/or other debris
and/or fluids removed from the wound bed by the negative pressure
pump 112 may be collected in a canister 114 located on the therapy
unit 102.
[0037] Operating the negative pressure pump 112 may therefore both
create a negative pressure at the wound bed and remove undesirable
fluid and debris from the wound bed. In some cases, operating the
negative pressure pump 112 may cause deformation of the wound bed
and/or provide other energy to the wound bed to facilitate
debridement and healing of the wound bed. As described in detail
below, the negative pressure pump 112 may be operated in accordance
with one or more dynamic pressure control approaches that may
facilitate wound healing.
[0038] The therapy unit 102 also includes an instillation pump 116.
The instillation pump 116 is configured to selectively provide
instillation fluid from the instillation fluid source 110 to the
dressing 104. The instillation pump 116 is operable to control the
timing and amount (volume) of instillation fluid provided to the
dressing 104. As described in detail below, the instillation pump
116 may be controlled in coordination with the negative pressure
pump 112 to provide one or more wound treatment cycles that may
facilitate wound healing.
[0039] The therapy unit 102 also includes an input/output device
118. The input/output device 118 is configured to provide
information relating to the operation of the NPIWT system 100 to a
user and to receive user input from the user. The input/output
device 118 may allow a user to input various preferences, settings,
commands, etc. that may be used in controlling the negative
pressure pump 112 and the instillation pump 116 as described in
detail below. The input/output device 118 may include a display
(e.g., a touchscreen), one or more buttons, one or more speakers,
and/or various other devices configured to provide information to a
user and/or receive input from a user.
[0040] As shown in FIG. 2, the therapy unit 102 is also shown to
include one or more sensors 200 and a control circuit 202. The
sensor(s) 200 may be configured to monitor one or more of various
physical parameters relating to the operation of the NPIWT system
100. For example, the sensor(s) 200 may measure pressure at the
vacuum tube 106, which may be substantially equivalent and/or
otherwise indicative of the pressure at the dressing 104. As
another example, the sensor(s) 200 may measure an amount (e.g.,
volume) of instillation fluid provided to the dressing 104 by the
instillation pump 116. The sensor(s) 200 may provide such
measurements to the control circuit 202.
[0041] The control circuit 202 is configured to control the
operation of the therapy unit 102, including by controlling the
negative pressure pump 112, the instillation pump 116, and the
input/output device 118. The control circuit 202 may receive
measurements from the sensor(s) 200 and/or user input from the
input/output device 118 and use the measurements and/or the user
input to generate control signals for the instillation pump 116
and/or the negative pressure pump 112. As described in detail with
reference to FIGS. 3-12 below, the control circuit 202 may control
the negative pressure pump 112 and the instillation pump 116 to
provide various combinations of various instillation phases, soak
periods, and negative pressure phases to support and encourage
wound healing.
[0042] Referring now to FIG. 3, graphical representations of
constant negative pressure therapy and dynamic pressure control
therapy are shown, according to exemplary embodiments. A first
graph 300 illustrates constant negative pressure therapy while a
second graph 302 illustrates dynamic pressure control therapy. The
graphs 300-302 show pressure at the dressing 104 on the vertical
axis and time on the horizontal axis. The graphs 300-302 both
include a pressure line 304 that illustrates the pressure at the
dressing 104 over time. The control circuit 202 is configured to
control the negative pressure pump 112 to achieve the pressure
trajectories illustrated by the pressure lines 304.
[0043] As illustrated by graph 300, the control circuit 202 may
control the negative pressure pump 112 to remove air, fluid,
debris, etc. from the dressing 104 to reduce the pressure at the
dressing 104 from atmospheric pressure to a target negative
pressure. The control circuit 202 may then control the negative
pressure pump 112 to maintain the pressure at the dressing 104 at
approximately the target negative pressure. In some embodiments,
the control circuit 202 may use pressure measurements from the
sensor(s) 200 as feedback to facilitate maintenance of the pressure
at approximately the target negative pressure. In the embodiment
shown, the target negative pressure may be any value from
approximately 25 mmHg to 200 mmHg. For example, in some
embodiments, the target negative pressure may be user-selectable
via the input/output device 118.
[0044] As illustrated by graph 302, the control circuit 202 may
control the negative pressure pump 112 to provide a cyclic
variation of negative pressure at the dressing 104. The control
circuit 202 may control the negative pressure pump 112 to remove
air, fluid, debris, etc. from the dressing 104 to reduce the
pressure at the dressing 104 from atmospheric pressure to a target
negative pressure (e.g., a high pressure value). The control
circuit 202 may then control the negative pressure pump 112 to
facilitate the pressure at the dressing 104 in returning to a low
pressure value. That is, the negative pressure pump 112 may allow
the pressure to drift back towards atmospheric pressure, for
example by putting the dressing in fluid communication with the
atmosphere, allowing air to leak into the dressing 104, and/or the
negative pressure pump 112 pumping air into the dressing 104. When
the pressure at the dressing 104 reaches a low pressure value
(e.g., as detected by the sensor(s) 200) the control circuit 202
may control the negative pressure pump 112 to remove air, fluid,
debris, etc. from the dressing 104 to reduce the pressure at the
dressing 104 from the low pressure value to the target negative
pressure (e.g., the high pressure value).
[0045] As illustrated by graph 302, the control circuit 202 may
cause the cycle between a low pressure value and a high pressure
value to be repeated multiple times. The low pressure value and the
high pressure value may be user selectable. For example, the low
pressure value may be approximately 25 mmHg and the high pressure
value may be in the range of approximately 50 mmHg to approximately
200 mmHg. In some embodiments, the low pressure value may be 0 mmHg
(i.e., atmospheric pressure). In other words, the control circuit
202 may control the negative pressure pump 112 to oscillate the
pressure at the dressing 104 across a pressure differential. The
pressure differential may be any value within a range between
approximately 5 mmHg and approximately 300 mmHg, for example 100
mmHg (i.e., an oscillation between 25 mmHg and 125 mmHg is an
oscillation across a pressure differential of 100 mmHg).
[0046] Although graphs 300 and 302 show linear transitions (i.e.,
constant slopes) between pressure values, it should be understood
that various other pressure trajectories (represented by pressure
line 304) may be provided by various embodiments. For example, the
pressure line 304 may take a sinusoidal form in alternative
embodiments of graph 302. Furthermore, while the example of graph
302 shows substantially equivalent rise times (i.e., the time for
pressure to change from the low pressure value to the high pressure
value) and fall times (i.e., the time for pressure to change from
the high pressure value to the low pressure value), it should be
understood that various relative rise times and fall times may be
used. For example, a rise time and/or fall time may be selected by
a user via the input/output device 118. The control circuit 202 may
control the negative pressure pump 112 to achieve the user-selected
rise time and/or fall time. Various additional embodiments of
dynamic pressure control are illustrated at FIGS. 10-12 and
described in detail with reference thereto.
Instillation, Soak, and Dynamic Pressure Control Cycle
[0047] Referring now to FIG. 4, a flowchart depicting a process 400
for treating a wound using the NPIWT system 100 of FIGS. 1-2 is
shown, according to an exemplary embodiment. Process 400 is shown
as a cycle through three phases, namely an instillation phase 402,
a soak phase 404, and a dynamic pressure control phase 406. The
control circuit 202 may be configured to control the instillation
pump 116 and the negative pressure pump 112 to execute process 400.
Advantageously, the process 400 may provide improved wound healing
as indicated by experimental results shown in FIG. 5 and described
with reference thereto below.
[0048] At the instillation phase 402, the control circuit 202
controls the instillation pump 116 to provide instillation fluid
from the instillation fluid source 110 to the dressing 104 via the
instillation tube 108. At the instillation phase 402, the control
circuit 202 may control the instillation pump 116 to provide a
particular amount (e.g., volume) of instillation fluid and/or to
provide instillation fluid for a particular duration of time.
Instillation fluid may thereby be placed in contact with the wound
bed. The amount of instillation fluid provided at the instillation
phase 402 and/or the duration of time of the instillation phase 402
may be user-selectable (e.g., by a doctor, nurse, caregiver,
patient) via the input/output device 118 and/or otherwise
customizable (e.g., for various wound types, for various types of
instillation fluid).
[0049] At the soak phase 404, the control circuit 202 provides a
soak period between the instillation phase 402 and the dynamic
pressure control phase 406. During the soak phase 404, the control
circuit 202 controls the instillation pump 116 to prevent
additional fluid from being added to the dressing 104 and prevents
the negative pressure pump 112 from operating. The soak phase 404
thereby provides a soak period during which the instillation fluid
added at the instillation phase 402 can soak into the wound bed,
for example to soften, loosen, dissolve, etc. unwanted scar tissue
or wound exudate. The duration of the soak period may be
user-selectable via the input/output device 118 and/or otherwise
customizable (e.g., for various wound types, for various types of
instillation fluid). For example, the soak period may have a
duration of between thirty seconds and ten minutes.
[0050] At the dynamic pressure control phase 406, the control
circuit 202 controls the negative pressure pump 112 to create a
cyclic variation of negative pressure at the dressing 104. The
negative pressure pump 112 may operate to cause the pressure at the
dressing 104 to oscillate between a low pressure value and a high
pressure value, for example as illustrated by pressure line 304 on
graph 302 of FIG. 3. The frequency of such oscillations may vary in
various embodiments and/or may be user-selectable via the
input/output device 118. The low pressure value, high pressure
value, and/or pressure differential may also be customizable (e.g.,
user-selectable via the input/output device 118). In some
embodiments, the instillation pump 116 is controlled to provide
instillation fluid to the dressing 104 during the dynamic pressure
control phase 406.
[0051] During the dynamic pressure control phase 406, the negative
pressure pump 112 is controlled to remove air, fluid, and/or debris
from the wound bed and the dressing 104. In some cases, the
negative pressure pump 112 may remove the instillation fluid added
at the instillation phase 402. The negative pressure pump 112 may
also remove tissue softened, dissolved, etc. by the instillation
fluid during the soak phase 404. Under dynamic pressure control
(e.g., as shown on graph 302 of FIG. 3), the cyclic variation of
negative pressure may provide additional energy to the wound bed to
facilitate debridement and encourage wound healing. The
instillation phase 402, the soak phase 404, and the dynamic
pressure control phase 406 thereby work together to provide
improved wound therapy.
[0052] As illustrated by FIG. 4, the control circuit 202 may
control the NPIWT system 100 to repeatedly cycle through the
sequence of the instillation phase 402, the soak phase 404, and the
dynamic pressure control phase 406. Various parameters (e.g.,
amount of instillation fluid provide, the length of the soak phase,
the low pressure value, the high pressure value, the oscillation
frequency) of the phases 402 may remain constant between cycles,
may vary between cycles, or some combination thereof. Accordingly,
the process 400 is highly configurable for various wound types,
wound sizes, patients, instillation fluids, dressings 104, etc.
Experimental Results
[0053] Referring now to FIG. 5, experimental results showing
improved wound healing using process 400 and the NPIWT system 100
are shown, according to an exemplary embodiment. An animal study
was conducted in which the NPIWT system 100 was used to treat
wounds under various control approaches, described below. After a
period of time, the thickness of granulation tissue on the wound
was then measured, which indicates an amount of wound healing
(i.e., thicker granulation tissue corresponds to more healing).
[0054] FIG. 5 shows a graph 500 and table 502 that indicate that
process 400 may provide higher rates of wound healing than
alternative wound therapy approaches. The table 502 displays the
data represented in the graph 500. The graph 500 includes a first
bar 504 that shows the mean granulation tissue thickness in the
experiment for a wound treated by the NPIWT system 100 using
constant negative pressure (e.g., 125 mmHg), for example as
illustrated by graph 302 of FIG. 3. The graph 500 also includes a
second bar 506 that shows the mean granulation tissue thickness in
the experiment for a wound treated by the NPIWT system 100 using
intermittent constant negative pressure, in which constant negative
pressure (e.g., 125 mmHg) is applied for intermittent time periods
separated by periods where the negative pressure pump 112 is turned
off. The graph 500 includes a third bar 508 that shows the mean
granulation tissue thickness in the experiment for a wound treated
by the NPIWT system 100 using dynamic pressure control, for example
as illustrated by graph 304 of FIG. 3 (e.g., with a low pressure
value of 25 mmHg and a high pressure value of 125 mmHg). Bars
504-508 correspond to negative pressure wound therapy without
instillation therapy.
[0055] The graph 500 also includes a fourth bar 510 that shows the
mean granulation tissue thickness in the experiment for a wound
treated by the NPIWT system 100 using a combination of instillation
therapy and constant negative pressure. The graph 500 also includes
a fifth bar 512 that shows the mean granulation tissue thickness
for a wound treated by the NPIWT system 100 executing process 400.
Accordingly, the fourth bar 510 and the fifth bar 512 correspond to
negative pressure wound therapy with instillation therapy.
[0056] As shown in the graph 500 of FIG. 5, the fifth bar 512 is
the largest, indicating that process 400 facilitates greater wound
healing relative to the wound therapy approaches corresponding to
the first bar 504, second bar 506, third bar 508, and fourth bar
510.
Dressing with Perforated Layer
[0057] Referring now to FIGS. 6-7, detailed views of an embodiment
of the dressing 104 are shown, according to an exemplary
embodiment. FIG. 6 shows a cross-sectional side view of the
dressing 104 while FIG. 7 shows a bottom view of the dressing 104
(i.e., a view of the wound-facing surface of the dressing 104 when
applied to a patient). The dressing 104 of FIGS. 6-7 may facilitate
debridement and cleansing of a wound bed when used in conjunction
with process 400 and/or various other wound therapy approaches
described herein. The dressing 104 of FIGS. 6-7 may substantially
similar to the dressing(s) shown and described in detail in "WOUND
DRESSING WITH SEMI-RIGID SUPPORT TO INCREASE DISRUPTION USING
PERFORATED DRESSING AND NEGATIVE PRESSURE WOUND THERAPY, Applicant
Docket Number VAC.1615PRO, U.S. Provisional Patent Application No.
62/757,365, filed Nov. 8, 2018, incorporated by reference herein in
its entirety.
[0058] As shown in FIGS. 6-7, the dressing 104 includes a drape 600
coupled to a connection pad 602, an intermediate layer 604 coupled
to the drape 600, a perforated layer 606 coupled to the
intermediate layer 604, and a wound contact layer 608 coupled to
the perforated layer 606. The drape 600 is sealable over a wound
bed to couple the dressing 104 to the wound bed in a substantially
airtight manner to allow a pressure differential to be maintained
across the drape 600. The connection pad 602 is coupled to the
drape 600, the vacuum tube 106 and the instillation tube 108. The
connection pad 602 is positioned at a passage 610 through the drape
600. The connection pad 602 allows for removal of air, fluid, wound
exudate, etc. from the dressing 104 via the vacuum tube 106 and
allows for addition of instillation fluid to the dressing 104 via
the instillation tube 108.
[0059] The drape 600 is positioned along the intermediate layer
604. The intermediate layer 604 may be a support layer and/or a
manifolding layer. The intermediate layer 604 allows air, fluid,
debris, etc. to flow therethrough, i.e., to flow between the
connection pad 602 and the perforated layer 606. The perforated
layer 606 is positioned along the intermediate layer 604 and
configured to allow a negative pressure to be distributed across
the wound bed and to allow fluid, debris, etc. to be pass
therethrough. A wound contact layer 608 may be coupled to the
perforated layer 606 and may be configured to minimize adherence of
the dressing 104 to the wound bed.
[0060] The perforated layer 606 includes multiple holes 612
extending therethrough. In various embodiments, various numbers of
the holes 612 are arranged in various positions on the perforated
layer 606. As described in detail below, when negative pressure is
established at the dressing 104, the wound bed may be caused to
deform into the holes 612 by the negative pressure. Deformation of
the wound bed into the multiple holes 612 may contribute to the
breakdown of scar tissue or other unwanted tissue or debris at the
wound bed. The perforated layer 606 may thereby facilitate
debridement and/or cleansing of the wound bed to promote wound
healing.
Wound Bed Deformation
[0061] Referring now to FIG. 8, a visualization of wound bed
deformation into the multiple holes 612 of the perforated layer 606
of the dressing 104 of FIGS. 6-7 under dynamic pressure control is
shown, according to an exemplary embodiment. FIG. 8 shows a
schematic diagram 800 illustrating that wound bed deformation may
be quantified by a measurement of a deformation height from a base
802 of the wound bed to a deformation peak 804 of the wound bed.
The deformation height may correspond to a vertical displacement
between a point on the wound bed aligned with one of the multiple
holes 612 and a point on the wound bed not aligned with one of the
multiple holes 612, such that the deformation height measures how
far the wound bed extends into the hole 612.
[0062] FIG. 8 also includes a graph 806 that illustrates
deformation height over time under dynamic pressure control. In the
example shown, the control circuit 202 controls the negative
pressure pump 112 to provide a cyclic variation of negative
pressure at the dressing 104 that acts on the wound bed. In this
example, the cyclic variation of negative pressure follows the
waveform shown in graph 302 of FIG. 3 and oscillates between a low
pressure value of 25 mmHg and a high pressure value of 125 mmHg.
Furthermore, in the example shown, the graph 806 is based upon
experimental results using a simulated wound material known as
Dermasol.
[0063] The graph 806 includes a deformation height line 808 that
shows that the deformation height approximately tracks the waveform
of graph 302. The deformation height increases as negative pressure
increases and decreases as negative pressure decrease. In the
example shown by the graph 806, the deformation height line 808
reaches maximums at approximately 2.2 millimeters and minimums at
approximately 1.0 millimeters. In other words, in the example
shown, the wound bed deforms by approximately 2.2 millimeters into
the holes 612 under high negative pressure and by approximately 1
millimeter under low negative pressure. FIG. 8 also includes a
first depiction 810 of the wound bed while at a maximum deformation
and a second depiction 812 of the wound bed while at a minimum
deformation.
[0064] The deformation of the wound bed may be characterized in
terms of the work provided to the wound bed and the elastic energy
stored in the deformed tissue. The following paragraphs describe
the Applicant's present understanding of the relationship between
applied negative pressure, wound bed deformation, work, and elastic
energy.
[0065] During negative pressure wound therapy, the tissue in the
wound bed is displaced by applied pressure. The work W performed by
the applied pressure is related to a change in the elastic energy
.DELTA.U stored in the deformation tissue as:
W=.DELTA.U. (1)
[0066] This relationship can be employed to predict tissue
deformations from a given applied pressure. To illustrate this, a
simple calculation may be performed using experimentally determined
values for a model wound material Dermasol. Given a constant value
of the applied pressure P, a model wound bed of initial height L
and made of Dermasol with Young's modulus E, a fractional change of
length .DELTA.L/L of a region with cross-sectional area A will
occur. The Applicant believes that the work performed by the
applied pressure and associated change in tissue elastic energy is
given by:
W = .intg. 0 .DELTA. V PdV = PA .intg. 0 .DELTA. L dy = A ( P )
.DELTA. L ; .DELTA. U = .intg. 0 .DELTA. L ( A L ) Eydy = A ( E 2
.DELTA. L L ) .DELTA. L . ( 2 ) ##EQU00001##
[0067] This relationship is validated with the experimentally
determined values reported in the following table:
TABLE-US-00001 Measurement Variable Value Pressure P 16665 Pa
Young's Modulus E 119110 Pa Undeformed Height L 14 mm Height
Deformation .DELTA.L 5 mm Cross-Sectional Area A 80 mm.sup.2
These values give:
W=(80*10.sup.-6)(1665)(5*10.sup.-3).apprxeq.7 mj;
.DELTA.U=(80*10.sup.-6)(119110/2 5/14)(5*10.sup.-3).apprxeq.9 mj.
(3)
[0068] While the work performed by the applied pressure and the
elastic energy in the deformed tissue are of the same magnitude,
there is an approximately 20% discrepancy. The resolution of this
discrepancy will require the following improvements: First, more
accurate measurement of the elastic properties of the Dermosol may
be required. The Young's modulus and Poisson's ration, the latter
having been neglected above in the analysis above for the sake of
simplicity, can be accurately determined using an oscillatory
rheometer. Second, inclusion of the deformation of the dressing may
also be required.
[0069] Knowing the elastic properties of Dermosol, the geometry of
the wound model, and the applied pressure, the displacement of the
wound is calculable. This face is reflected in the relationships by
Equations (2), i.e.,
P = E 2 .DELTA. L L .DELTA. L = 2 LP E . ##EQU00002##
[0070] Here the displacement .DELTA.L is a function of the initial
geometry L, the applied pressure P, and the elastic property E.
Using more detailed information from the rheometry measurements
suggested above and the computational method Finite Element
Analysis, the deformation field of the wound model may be
calculated. This technique may be a useful tool for optimizing
negative pressure wound therapy products, for example the NPIWT
system 100 and components thereof.
[0071] The total amount of work done on a wound bed may also be
calculated using this approach. For example, at 9 mJ per
perforation (i.e., as calculated at Equations (3)) and a dressing
104 with twenty-three holes 612, the negative pressure pump 112
does approximately 207 mJ of work on the wound bed per cycle of the
cyclic variation of negative pressure (i.e., for each period of the
waveform shown on graph 302). If five cycles are provided in a
phase (e.g., during the dynamic pressure control phase 406) the
work increases to approximately 5*207 mJ=1035 mJ for the phase. The
negative pressure pump 112 may therefore do substantially more work
on the wound bed under dynamic pressure control than under a
constant negative pressure approach.
NPIWT System with Scrub Cycle and Instillation Cycle
[0072] Referring now to FIG. 9, a process 900 for providing wound
therapy with the NPIWT system 100 is shown, according to an
exemplary embodiment. The control circuit 202 may be configured to
control the instillation pump 116 and the negative pressure pump
112 to execute process 900. In some embodiments, the process 900 is
carried out with a dressing 104 that includes the perforated layer
606 with holes 612 as in FIGS. 6-7. As described in detail below,
provides 900 provides wound therapy having a scrub cycle and an
instillation cycle.
[0073] At step 902, wound therapy is initiated. The dressing 104 is
sealed over a wound bed and coupled to the therapy unit 102 by the
vacuum tube 106 and the instillation tube 108. To cause wound
therapy to be initiated, a user may input a command via the
input/output device 118 to initiate therapy (e.g., to turn on). In
response, the control circuit 202 may be activated and may proceed
to control the instillation pump 116 and the negative pressure pump
112 as described in the following paragraphs.
[0074] At step 904, the control circuit 202 determines whether to
initiate a scrub cycle. The scrub cycle includes steps 906-914 of
process 900, described in detail below. The scrub cycle provides
enhanced scrubbing, debridement, cleansing, etc. of the wound bed.
Accordingly, the control circuit 202 may determine to initiate the
scrub cycle based on an indication that the wound bed requires
scrubbing, debridement, cleansing, etc., for example based on
information about the type of wound being treated. In some
embodiments, the control circuit 202 causes the input/output device
118 to prompt a user to select whether to initiate the scrub
cycle
[0075] If the control circuit 202 determines that the scrub cycle
will be initiated, at step 906 the control circuit 202 controls the
instillation pump 116 to provide an instillation phase. During step
906 (i.e., during the instillation phase), instillation fluid is
added to the dressing 104. The control circuit 202 may control the
instillation pump 116 to provide a particular amount of the
instillation fluid to the dressing 104 and/or provide instillation
fluid to the dressing 104 for a particular amount of time. The
amount of fluid added and/or the duration of the instillation phase
may be user-selectable via the input/output device 118 and/or
otherwise customizable (e.g., for various wound types, for various
types of instillation fluid).
[0076] At step 908, the instillation fluid added at step 906 is
allowed to soak into the wound bed in a soak phase. During the soak
phase (i.e., at step 908), the control circuit 202 may control the
instillation pump 116 to prevent instillation fluid from being
added to the dressing 104 and may prevent operation of the negative
pressure pump 112. The control circuit 202 thereby provides a soak
period during which the instillation fluid added at step 906 can
soak into the wound bed, for example to soften, loosen, dissolve,
etc. unwanted scar tissue or wound exudate. The duration of the
soak period may be user-selectable via the input/output device 118
and/or otherwise customizable (e.g., for various wound types, for
various types of instillation fluid). For example, the soak period
may have a duration of between thirty seconds and ten minutes.
[0077] At step 910, the control circuit 202 controls the negative
pressure pump 112 to provide a cyclic variation of negative
pressure at the dressing 104 and the wound bed in a dynamic
pressure control phase. In embodiments where the dressing 104
includes holes 612 as in FIG. 6, the wound bed may be deformed into
the holes 612 during step 910. For example, the wound deformation
height may increase as the negative pressure at the dressing 104
increases and may decrease as the negative pressure at the dressing
104 decreases. In some embodiments, as described above with
reference to FIG. 8, the negative pressure may do work on the wound
bed in a range of approximately 7 mJ to 9 mJ per hole 612 for each
cycle of the cyclic variation of negative pressure (e.g., for each
period of the waveform shown on graph 302 of FIG. 3). In various
embodiments, the negative pressure may do work on the wound bed in
a range of approximately 2 mJ and 30 mJ per hole 612 for each
cycle. As another example, with a diameter of the holes 612 of
approximately 10 mm and a negative pressure of 125 mmHg, work in a
range of approximately 2 mJ to 3 mJ can be achieved. Higher amounts
of work may be provided by increasing the size of the holes 612 and
by increasing the pressure (in absolute value). The combination of
dynamic pressure control and the perforated layer 606 of the
dressing 104 provides increased scrubbing and debridement of the
wound bed at step 910. Accordingly, step 910 may cause the
separation of a substantial amount of debris, scar tissue, etc.
from the wound bed.
[0078] In some embodiments, the dynamic pressure control phase of
step 910 includes controlling the negative pressure pump 112 to
provide a waveform having hold periods at high pressure values
and/or low pressure values, for example as shown in FIG. 10 and
described with reference thereto. In some embodiments, the dynamic
pressure control phase of step 910 includes controlling the
negative pressure pump 112 to provide an aggressive cleanse
waveform, for example as shown in FIG. 11 and described with
reference thereto. In some embodiments, the dynamic pressure
control phase of step 910 includes varying a high pressure value
and/or pressure differential of the cyclic variation of negative
pressure over time, for example as shown in FIG. 12 and described
in detail with reference thereto. The duration of step 910 may be
user-selectable and/or otherwise customizable. In various
embodiments, the dynamic pressure control phase may have a duration
between one minute and three hours, for example three minutes. In
some embodiments, the dynamic pressure control phase of step 910
includes controlling the instillation pump 116 to provide
instillation fluid to the dressing 104 during step 910.
[0079] At step 912, the control circuit 202 determines whether to
continue the scrub cycle. In some embodiments, the control circuit
202 may determine whether to continue the scrub cycle based on a
preset number of desired scrub cycles. For example, the control
circuit 202 may count the number of times that steps 906-910 are
completed and continue the scrub cycle until that number reaches a
preset threshold (e.g., a threshold number input by a user). In
other embodiments, at step 912 the control circuit 202 may cause
the input/output device 118 to prompt a user for input indicating
whether to continue the scrub cycle and determine whether to
content the scrub cycle based on the user input.
[0080] If the control circuit 202 makes a determine a determination
to continue the scrub cycle, at step 914 the control circuit 202
controls the negative pressure pump 112 to provide a fluid removal
phase. During the fluid removal phase, the negative pressure pump
112 is controlled to remove fluid, debris, etc. from the dressing
104. The fluid, debris, etc. removed from the dressing 104 by the
negative pressure pump 112 at step 914 may include the instillation
fluid added at step 906 and debris, scar tissue, etc. separated
from the wound bed at step 910. Step 914 thereby provides a fluid
removal phase in which undesirable fluid and debris is removed from
the dressing 104 and prepares NPIWT system 100 to repeat the scrub
cycle.
[0081] Following the fluid removal phase of step 914, the process
900 returns to cycle through step 906, step 908, and step 910. The
scrub cycle (i.e., steps 906-914) may be repeated any number of
times until, at an instance of step 912, the control circuit 202
determines that the scrub cycle will no longer be continued.
[0082] If the control circuit 202 determines that the scrub cycle
will not be continued at step 912, process 900 proceeds to step 916
where a constant negative pressure phase is provided to initiate an
instillation cycle (steps 916-920). At step 916, the control
circuit 202 controls the negative pressure pump 112 to provide an
approximately constant negative pressure (e.g., 125 mmHg, 100 mmHg,
etc.), for example as shown in graph 300 of FIG. 3. The control
circuit 202 may receive pressure measurements from the sensor(s)
200 for use as feedback in a control loop for the negative pressure
pump 112. The negative pressure pump 112 may remove fluid, debris,
etc. provided to the dressing 104 and/or separated or exuded from
the wound bed. The duration of the constant negative pressure phase
may be user-selectable via input/output device 118 and/or otherwise
customizable.
[0083] At step 918, the control circuit 202 provides an
instillation phase by controlling the instillation pump 116 to
provide instillation fluid to the dressing 104. In some
embodiments, the control circuit 202 behaves substantially the same
at step 918 is as at step 906. The instillation pump 116 may be
controlled to provide a particular amount of the instillation fluid
to the dressing 104 and/or provide instillation fluid to the
dressing 104 for a particular amount of time. The amount of fluid
added and/or the duration of the instillation phase may be
user-selectable via the input/output device 118 and/or otherwise
customizable (e.g., for various wound types, for various types of
instillation fluid).
[0084] At step 920, the control circuit 202 provides a soak phase
by controlling the instillation pump 116 to prevent the addition of
instillation fluid to the dressing 104 for a soak period and to
prevent operation of the negative pressure pump 112 for the soak
period. In some embodiments, the control circuit 202 behaves
substantially the same at step 920 as at step 908. The control
circuit 202 provides a soak period during which the instillation
fluid added at step 918 can soak into the wound bed, for example to
soften, loosen, dissolve, etc. unwanted scar tissue or wound
exudate or to provide other therapy to the wound bed. The duration
of the soak period may be user-selectable via the input/output
device 118 and/or otherwise customizable (e.g., for various wound
types, for various types of instillation fluid). For example, the
soak period may have a duration of between thirty seconds and ten
minutes.
[0085] At step 922, the control circuit 202 determines whether to
return to the scrub cycle or to repeat the instillation cycle
(i.e., steps 916-920). For example, the control circuit 202 may
repeat the instillation cycle for a preset or user-selected number
of times before repeating the instillation cycle. In some
embodiments, at step 922 the control circuit 202 causes the
input/output device 118 to prompt a user to input an indication of
whether to return to the scrub cycle or to repeat the instillation
cycle. If the control circuit 202 makes a determination to not
return to the scrub cycle, process 900 returns to step 916 to
restart the instillation cycle. If the control circuit 202 makes a
determination to return to the scrub cycle, the process 900 returns
to step 914 to reenter the scrub cycle.
[0086] The control circuit 202 may thereby control the instillation
pump 116 and the negative pressure pump 112 to provide various
numbers of scrub cycles and instillation cycles in various orders.
Furthermore, it should be understood that the duration of each
phase (i.e., steps 906, 908, 910, 914, 916, 918, and 920) is highly
variable. For example, the duration of one or more phases may
change between sequential cycles. Various other parameters (e.g.,
low pressure values, high pressure values, frequency, waveform,
amount of instillation fluid, etc.) may also vary between cycles.
Accordingly, process 900 is highly configurable and customizable to
provide negative pressure and instillation wound therapy well
suited to a variety of wound types, patients, stages of healing,
etc.
Pressure Control Waveforms
[0087] Referring now to FIG. 10 an alternative embodiment of a
dynamic pressure control waveform is shown, according to an
exemplary embodiment. FIG. 10 shows a graph 1000 that includes a
pressure line 1002 that charts negative pressure over time. In the
embodiment of FIG. 10, the pressure line 1002 increases from
atmospheric pressure to a high pressure value (e.g., 125 mmHg of
negative pressure) and remains at the high pressure value for a
first hold period 1004 before decreasing to a low pressure value
(e.g., 25 mmHg). The pressure line 1002 then remains at the low
pressure value for a second hold period 1006 before returning to
the high pressure value. This cycle may be repeated any number of
times. The graph 1000 also includes a deformation height line 1008
that charts the deformation height of the wound bed over time in
response to the changes in negative pressure.
[0088] The control circuit 202 may control the negative pressure
pump 112 to provide negative pressure that substantially tracks the
pressure line 1002 of FIG. 10. In such a case, the first hold
period 1004 may allow time for the wound bed to reach a maximum
deformation height (e.g., shown as 2.2 mm) before the negative
pressure is reduced. The second hold period 1006 may allow the
wound bed to reach a minimum deformation height (e.g., shown as 1
mm) before the negative pressure is increased. The dynamic pressure
control waveform of FIG. 10 thereby accounts for a lag time between
a change in pressure and a change in tissue deformation, which may
help to maximize the amount of work done on the wound bed. In
various embodiments, the first hold period 1004 and the second hold
period 1006 may have the same duration or different durations. In
various embodiments, the maximum deformation height and the minimum
deformation height have various values. A dynamic pressure control
approach having hold periods 1004, 1006 may be applied in process
400 (at dynamic pressure control phase 406) and/or process 900 (at
dynamic pressure control phase 910), and may be used with the
perforated layer 606 of the dressing 104.
[0089] Referring now to FIG. 11, a graphical representation of
aggressive cleanse pressure control is shown, according to an
exemplary embodiment. FIG. 11 includes a graph 1100 that charts
negative pressure over time. Graph 1100 includes a dynamic pressure
control line 1102 and an aggressive cleanse pressure control line
1104. The dynamic pressure control line 1102 corresponds to the
pressure line 304 on graph 302 of FIG. 3 and is included in graph
1100 for the sake of comparison to the aggressive cleanse pressure
control line 1104. The dynamic pressure control line 1102 shows
that, under dynamic pressure control, the control circuit 202 may
control the negative pressure pump 112 to draw a negative pressure
at the dressing 104 from atmospheric pressure to a high pressure
value, allow the negative pressure to return to a low pressure
value, draw the negative pressure back to the high pressure value,
and so on. In other words, the dynamic pressure control line 1102
illustrates a waveform having a frequency and an amplitude (i.e., a
pressure differential). The amplitude of the dynamic pressure
control line 1102 ranges from a minimum at the low pressure value
to a maximum at the high pressure value.
[0090] The aggressive cleanse pressure control line 1104
illustrates an alternative pressure control approach which may do
an increased amount of work on the wound bed and provide for
increased debridement of the wound bed. The aggressive cleanse
pressure control line 1104 illustrates that the control circuit 202
may control the negative pressure pump 112 to draw a negative
pressure at the dressing 104 from atmospheric pressure to a high
pressure value, allow the dressing 104 to return to atmospheric
pressure, draw negative pressure at the dressing 104 from
atmospheric pressure to a high pressure value, allow the dressing
104 to return to atmospheric pressure, and so on. The control
circuit 202 thereby controls the negative pressure pump 112 to
provide a cyclic variation of negative pressure that oscillates
between a high pressure value and atmospheric pressure.
[0091] Accordingly, the aggressive cleanse pressure control line
1104 depicts a waveform with a greater amplitude (i.e., greater
pressure differential) as compared to the waveform of the dynamic
pressure control line 1102. Furthermore, the aggressive cleanse
pressure control line 1104 depicts a waveform with a greater
frequency (shorter period) as compared to the waveform of the
dynamic pressure control line 1102. Because of the greater
amplitude and frequency, aggressive cleanse pressure control may
provide more energy to the wound bed and cause increased scrubbing
and debridement of the wound bed. In some embodiments, aggressive
cleanse pressure control may be used in process 400 (at dynamic
pressure control phase 406) and/or process 900 (at dynamic pressure
control phase 910). In some embodiments, aggressive cleanse
pressure control is used with the perforated layer 606 of the
dressing 104.
[0092] Referring now to FIG. 12, a graphical representation of
dynamic pressure control with a variable high pressure value is
shown, according to an exemplary embodiment. As illustrated by
pressure line 1200 on graph 1202 of FIG. 12, dynamic pressure
control may provide a cyclic variation of negative pressure that
includes multiple cycles between a low pressure value and a high
pressure value. In the example of FIG. 12, the high pressure value
changes between a first cycle and a second cycle of the multiple
cycles. In various embodiments, the pressure differential may
change between the first and second cycles in a variety of ways. In
the example of FIG. 12, the high pressure value oscillates over
time between a minimum high pressure value (e.g., 125 mmHg) and a
maximum high pressure value (e.g., 200 mmHg). The control circuit
202 may be configured to control the negative pressure pump 112 to
provide the negative pressure depicted by the pressure line 1200 of
FIG. 12. Changing the high pressure value over time as in FIG. 12
may facilitate wound healing by preventing the wound bed from
adapting to a particular high pressure value. Dynamic pressure
control with a variable high pressure value as illustrated by
pressure line 1200 may be used in process 400 (at dynamic pressure
control phase 406) and/or process 900 (at dynamic pressure control
phase 910). In some embodiments, dynamic pressure control with a
variable high pressure value is used with the perforated layer 606
of the dressing 104.
[0093] FIGS. 3 and 10-12 show various dynamic pressure control
waveforms according to various embodiments. The control circuit 202
may be configured to control the negative pressure pump 112 to
provide negative pressure at the dressing 104 that substantially
tracks one or more of these waveforms and/or combinations thereof.
For example, the hold periods of the pressure line 1002 FIG. 10 may
be combined with the variable high pressure value of the pressure
line 1200 of FIG. 12 to provide hold periods at varying high
pressure values. Many such combinations and adaptations are
possible.
Configuration of Exemplary Embodiments
[0094] Although the figures show a specific order of method steps,
the order of the steps may differ from what is depicted. Also two
or more steps can be performed concurrently or with partial
concurrence. Such variation will depend on the software and
hardware systems chosen and on designer choice. All such variations
are within the scope of the disclosure. Likewise, software
implementations could be accomplished with standard programming
techniques with rule based logic and other logic to accomplish the
various connection steps, calculation steps, processing steps,
comparison steps, and decision steps.
[0095] The construction and arrangement of the systems and methods
as shown in the various exemplary embodiments are illustrative
only. Although only a few embodiments have been described in detail
in this disclosure, many modifications are possible (e.g.,
variations in sizes, dimensions, structures, shapes and proportions
of the various elements, values of parameters, mounting
arrangements, use of materials, colors, orientations, etc.). For
example, the position of elements can be reversed or otherwise
varied and the nature or number of discrete elements or positions
can be altered or varied. Accordingly, all such modifications are
intended to be included within the scope of the present disclosure.
The order or sequence of any process or method steps can be varied
or re-sequenced according to alternative embodiments. Other
substitutions, modifications, changes, and omissions can be made in
the design, operating conditions and arrangement of the exemplary
embodiments without departing from the scope of the present
disclosure.
[0096] As utilized herein, the terms "approximately," "about,"
"substantially", and similar terms are intended to have a broad
meaning in harmony with the common and accepted usage by those of
ordinary skill in the art to which the subject matter of this
disclosure pertains. It should be understood by those of skill in
the art who review this disclosure that these terms are intended to
allow a description of certain features described and claimed
without restricting the scope of these features to the precise
numerical ranges provided. Accordingly, these terms should be
interpreted as indicating that insubstantial or inconsequential
modifications or alterations of the subject matter described and
claimed are considered to be within the scope of the disclosure as
recited in the appended claims.
[0097] As used herein, the term "circuit" may include hardware
structured to execute the functions described herein. In some
embodiments, each respective "circuit" may include machine-readable
media for configuring the hardware to execute the functions
described herein. The circuit may be embodied as one or more
circuitry components including, but not limited to, processing
circuitry, network interfaces, peripheral devices, input devices,
output devices, sensors, etc. In some embodiments, a circuit may
take the form of one or more analog circuits, electronic circuits
(e.g., integrated circuits (IC), discrete circuits, system on a
chip (SOCs) circuits, etc.), telecommunication circuits, hybrid
circuits, and any other type of "circuit." In this regard, the
"circuit" may include any type of component for accomplishing or
facilitating achievement of the operations described herein. For
example, a circuit as described herein may include one or more
transistors, logic gates (e.g., NAND, AND, NOR, OR, XOR, NOT, XNOR,
etc.), resistors, multiplexers, registers, capacitors, inductors,
diodes, wiring, and so on).
[0098] The "circuit" may also include one or more processors
communicably coupled to one or more memory or memory devices. In
this regard, the one or more processors may execute instructions
stored in the memory or may execute instructions otherwise
accessible to the one or more processors. In some embodiments, the
one or more processors may be embodied in various ways. The one or
more processors may be constructed in a manner sufficient to
perform at least the operations described herein. In some
embodiments, the one or more processors may be shared by multiple
circuits (e.g., circuit A and circuit B may comprise or otherwise
share the same processor which, in some example embodiments, may
execute instructions stored, or otherwise accessed, via different
areas of memory). Alternatively or additionally, the one or more
processors may be structured to perform or otherwise execute
certain operations independent of one or more co-processors. In
other example embodiments, two or more processors may be coupled
via a bus to enable independent, parallel, pipelined, or
multi-threaded instruction execution. Each processor may be
implemented as one or more general-purpose processors, application
specific integrated circuits (ASICs), field programmable gate
arrays (FPGAs), digital signal processors (DSPs), or other suitable
electronic data processing components structured to execute
instructions provided by memory. The one or more processors may
take the form of a single core processor, multi-core processor
(e.g., a dual core processor, triple core processor, quad core
processor, etc.), microprocessor, etc. In some embodiments, the one
or more processors may be external to the apparatus, for example
the one or more processors may be a remote processor (e.g., a cloud
based processor). Alternatively or additionally, the one or more
processors may be internal and/or local to the apparatus. In this
regard, a given circuit or components thereof may be disposed
locally (e.g., as part of a local server, a local computing system,
etc.) or remotely (e.g., as part of a remote server such as a cloud
based server). To that end, a "circuit" as described herein may
include components that are distributed across one or more
locations. The present disclosure contemplates methods, systems and
program products on any machine-readable media for accomplishing
various operations. The embodiments of the present disclosure can
be implemented using existing computer processors, or by a special
purpose computer processor for an appropriate system, incorporated
for this or another purpose, or by a hardwired system. Embodiments
within the scope of the present disclosure include program products
comprising machine-readable media for carrying or having
machine-executable instructions or data structures stored thereon.
Such machine-readable media can be any available media that can be
accessed by a general purpose or special purpose computer or other
machine with a processor. By way of example, such machine-readable
media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical
disk storage, magnetic disk storage or other magnetic storage
devices, or any other medium which can be used to carry or store
desired program code in the form of machine-executable instructions
or data structures and which can be accessed by a general purpose
or special purpose computer or other machine with a processor.
Combinations of the above are also included within the scope of
machine-readable media. Machine-executable instructions include,
for example, instructions and data which cause a general purpose
computer, special purpose computer, or special purpose processing
machines to perform a certain function or group of functions.
* * * * *